I contacted the dealer and got the VIN for one of the vehicles he's selling, my insurer did a lookup on that VIN and it wasn't in the database either so still no go. I contacted another insurance company and went through the same process with the same result. The provincial government has a "Consumer Advocate for Insurance" and I have filled out the form on their website.
I thought about just insuring it under the gas model number but I'm not willing to deal with the possibility that it could invalidate my coverage or that I would get the value of the gas model if it were to get totaled or whatever. I don't think they'll insure it without the VIN lookup anyway. The dealer said he has sold two previously and they got insurance so there's someone out there willing to insure them, hopefully I can find out who and if they aren't Quebec-only I'll have a fallback.
On a brighter note, I went into the local Chevy dealer that does Volt servicing and they pulled up the Spark EV on their service computer system and said there would be no problem servicing it. So that's reassuring. I'm going to Montreal this weekend and will test drive the car on Monday. If that goes okay and I can get insurance then I'm going to buy.